H. Firouzabadi et al. / Journal of Molecular Catalysis A: Chemical 347 (2011) 38–45
39
efficiency of the catalyst from different views. Even though pal-
2.4. Reusability of the catalyst
ladium has widespread utility for this reaction, it has some
limitations such as being expensive and also some precautionary
measures should be taken into account such as air-sensitivity, tox-
icity of some of its salts and also the amount of Pd leaching, which
problems, heterogenization of the catalyst and using nanoparti-
cles of palladium are good options. It was reported that palladium
nanoparticles of different origins have been used in this reaction
[17]. However, the design and generation of new nanoparticles, on
easily available, cheap, and nontoxic naturally occurring beds are
of great values from different aspects.
After completion of the reaction in the first run, ethyl acetate
(5 mL) was added to the reaction mixture to extract the organic
compounds. The ethyl acetate phase was removed by a syringe and
the catalyst was dried under nitrogen flow. After complete drying,
the catalyst was charged into another vessel containing the starting
materials. The consecutive reaction was performed under the same
conditions as discussed in the preceding general procedure. The
2.5. Spectral data
In recent years, we have paid attention to the use of transition
metal catalyst in different naturally compatible media for C–C and
C–X bond formation [18]. In the current work, we have established a
simple approach to gram-scale preparation of palladium nanopar-
ticles supported on gelatin, as an edible, ecofriendly, degradable in
nature and cheap protein. The supported nanoparticles have been
successfully applied for solvent-free Mizoroki–Heck reaction as a
recyclable catalyst.
(3a): [18e] 1H NMR (CDCl3, 250 MHz): ı (ppm): 0.90 (t, 3H,
J = 7.5 Hz), 1.37 (sex, 2H, J = 7.7), 1.65 (quint, 2H, J = 7.5), 4.17 (t, 2H,
J = 6.75 Hz), 6.53 (d, 1H, J = 16 Hz), 7.60 (d, 2H, J = 8.75), 7.63 (d, 1H,
J = 16.25), 8.18 (d, 2H, J = 8.75); 13C NMR (CDCl3, 62.9 MHz): ı (ppm):
13.69, 19.14, 30.66, 64.88, 122.59, 124.14, 128.59, 140.58, 141.55,
166.09.
(3b): [19] 1H NMR (CDCl3, 250 MHz): ı (ppm): 0.87 (t, 3H,
J = 7.25 Hz), 1.37 (sex, 2H, J = 7.5), 1.65 (quint, 2H, J = 6.5), 4.17 (t, 2H,
J = 7 Hz), 6.40 (d, 1H, J = 14 Hz), 7.31–7.42 (m, 3H), 7.58–7.74 (m, 3H),
8.05 (d, 1H, J = 8.25 Hz), 8.40 (d, 1H, J = 15.75 Hz); 13C NMR (CDCl3,
62.9 MHz): ı (ppm): 13.81, 19.27, 30.84, 64.53, 120.93, 123.38,
124.45, 124.98, 125.44, 125.84, 126.20, 126.40, 126.60, 126.83,
128.72, 129.12, 130.46, 131.42, 131.81, 133.68, 141.56, 166.97.
(3c): [18e] 1H NMR (CDCl3, 250 MHz): ı (ppm): 0.89 (t, 3H,
J = 7.5 Hz), 1.35 (sex, 2H, J = 7.5 Hz), 1.61 (quint, 2H, J = 5 Hz), 3.76
(s, 3H), 4.13 (t, 2H, J = 6.7), 6.24 (d, 1H, J = 15 Hz), 6.83 (d, 1H,
J = 5 Hz), 7.40 (d, 2H, J = 5 Hz), 7.56 (d, 1H, J = 16 Hz); 13C NMR (CDCl3,
62.9 MHz): ı (ppm): 13.75, 19.20, 30.80, 55.35, 64.25, 114.28,
115.76, 129.67, 144.19, 161.30.
2. Experimental
2.1. General
All chemicals were purchased from Merck, Fluka or Acros Chem-
ical Companies and used without any further purification. NMR
spectra were recorded with a Bruker Avance DPX-250 spectrome-
ter (1H NMR 250 MHz and 13C NMR 62.9 MHz) in pure deuteriated
chloroform with tetramethylsilane (TMS) as the internal standard.
UV spectra (PerkinElmer, Lambda 25, UV/Vis spectrometer) were
used to ensure the complete conversion of Pd(II) to Pd(0). Scanning
electron micrographs were obtained by SEM (SEM, XL-30 FEG SEM,
Philips, at 20 kV). Transmission electron microscope, TEM (Philips
CM10) was also used to obtain TEM images. Atomic force micro-
scope, AFM (DME, Dual ScopeTM DS 95-200-E) was also used to
obtain AFM images. The amount of palladium nanoparticles sup-
ported on gelatin was measured by ICP analyzer (Varian, Vista-pro)
and atomic absorption spectroscopy.
(3d): [18e] 1H NMR (CDCl3, 250 MHz): ı (ppm): 0.97 (t, 3H,
J = 7.25 Hz), 1.45 (sex, 2H, J = 7.5 Hz), 1.67 (quint, 2H, J = 5 Hz), 4.23 (t,
2H, J = 7.5 Hz), 6.54 (dd, 1H, J = 16 Hz, Jꢀ = 6.2 Hz), 7.67 (m, 3H), 8.24
(m, 2H); 13C NMR (CDCl3, 62.9 MHz): ı (ppm): 13.70, 19.15, 30.67,
64.90, 122.59, 124.15, 128.60, 140.58, 141.56.
(3e): [18e] 1H NMR (CDCl3, 250 MHz): ı (ppm): 0.85 (t, 3H,
J = 4.7 Hz), 1.32 (sex, 2H, J = 4.3 Hz), 1.56 (quint, 2H, J = 2.5 Hz), 2.24
(s, 3H), 4.09 (t, 2H, J = 5 Hz), 6.30 (dd, 1H, J = 16 Hz, Jꢀ = 5.9 Hz), 7.06
(m, 2H), 7.29 (m, 2H), 7.52 (dd, 1H, J = 18.2 Hz, Jꢀ = 5.5 Hz),); 13C
NMR (CDCl3, 62.9 MHz): ı (ppm): 13.75, 19.21, 21.41, 30.80, 64.28,
117.16, 128.34, 129.57, 131.73, 140.55, 144.52, 167.22.
2.2. Large scale synthesis of palladium nanoparticles supported
on gelatin
(3f): [18e] 1H NMR (CDCl3, 250 MHz): ı (ppm): 0.85 (t, 3H,
J = 2.5 Hz), 1.32 (sex, 2H), 1.57 (quint, 2H), 2.30 (s, 3H), 4.11 (t, 2H),
6.27 (dd, 1H, J = 15.9 Hz, Jꢀ = 4.8 Hz), 7.11 (m, 3H), 7.41 (m, 1H), 7.84
(dd, 1H, J = 13.7 Hz, Jꢀ = 4.3 Hz); 13C NMR (CDCl3, 62.9 MHz): ı (ppm):
13.76, 18.96, 19.74, 30.79, 64.36, 119.26, 126.31, 129.94, 130.75,
133.40, 137.56, 142.20, 167.09.
Gelatin (1 g) was first dissolved in water (100 mL) at room tem-
perature. To this solution was added a solution of PdCl2 (100 mL,
1 mM) and diluted with water (100 mL). Then, the solution was
refluxed for 5 h to ensure the complete conversion of Pd(II) to Pd(0).
The solution was cooled down to room temperature. Evaporation
of the solvent was performed under a flow of air over night and
dried in vacuum for 24 h to give a dark grayish solid material.
(3g): [18e] 1H NMR (CDCl3, 250 MHz): ı (ppm): 0.89 (t, 3H,
J = 7.25 Hz), 1.35 (sex, 2H, J = 7.5 Hz), 1.64 (quint, 2H, J = 6.7), 4.16 (t,
2H, J = 6.5 Hz), 6.48 (d, 1H, J = 16 Hz), 7.59, (m, 5H); 13C NMR (CDCl3,
62.9 MHz): ı (ppm): 13.68, 19.12, 27.82, 30.64, 64.75, 113.27,
118.31, 121.84, 128.35, 132.58, 138.55, 142.03, 166.14.
2.3. General procedure for Mizoroki–Heck reaction using
Pd-nanoparticles supported on gelatin
(3h): [18e] 1H NMR (CDCl3, 250 MHz): ı (ppm): 0.90 (t, 3H,
J = 7.5 Hz), 1.39 (sex, 2H, J = 7.5 Hz), 1.61 (quin, 2H, J = 6 Hz), 4.17
(t, 2H, J = 5.5 Hz), 6.53 (d, 1H, J = 15 Hz), 7.52 (d, 1H, J = 15 Hz), 8.82
(s, 2H), 9.13 (s, 1H); 13C NMR (CDCl3, 62.9 MHz): ı (ppm): 13.68,
(3i): [19] 1H NMR (CDCl3, 250 MHz): ı (ppm): 7.02–8.11 (m,
12H); 13C NMR (CDCl3, 62.9 MHz): ı (ppm): 123.65, 123.81, 125.73,
125.86, 126.12, 126.72, 127.81, 128.07, 128.65, 128.78, 131.43,
131.79, 133.76, 135.04, 137.65.
Aryl halide (1 mmol) and alkene (1.5 mmol) were added to a
flask containing gelatin supported Pd-nanoparticles (0.05 g of the
gelatin-catalyst, contains 0.0045 mmol of palladium) and nPr3N
(1.5 mmol, 0.29 mL) in the absence of solvent. The mixture was
stirred at 140 ◦C in the air. After completion of the reaction (moni-
vessel. The catalyst was separated by simple filtration. Water (3×
15 mL) was added to the ethyl acetate phase and decanted. Then
the organic phase was dried over anhydrous Na2SO4. Evapora-
tion of the solvent gave the desired products in excellent yields
(Table 2).
(3j): [18e] 1H NMR (CDCl3, 250 MHz): ı (ppm): 2.32 (s, 3H), 6.89
(d, 1H, J = 16.25), 7.06–7.29 (m, 7H), 7.40–7.52 (m, 3H); 13C NMR
(CDCl3, 62.9 MHz): ı (ppm): 19.99, 124.95,125.44, 126.28, 126.61,